By default Cloud Custodian generates CloudWatch metrics on each policy for
the number of resources that matched the set of filters,
the time to retrieve and filter the resources, and the time to
execute actions.

In practice this number of matching resources allows for generating
enough metrics to put together useful dashboards over policies
in CloudWatch custom dashboards.

Additionally some filters and actions may generate their own metrics.

In order to enable metrics output, the boolean metrics
flag needs to be specified when running Cloud Custodian: